[BE] - remove dummy sceneId from the API

[aclegg3]

Motivation and Context

Multi-scene dummy API has been around for awhile. Cleaning it up.

How Has This Been Tested

CI

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[0mdc]

Great stuff! Thanks for doing this!

Do we currently have a need for SceneManager?

[aclegg3]

Do we currently have a need for SceneManager?

It plays a minor role currently in managing the distinction between the semantic and RGBD SceneGraphs, but I don't think we actually need it long term. In either case, that is separate enough to warrant it's own PR, so let's chat offline and consider it a follow-up.